Pancreatic cancer is a uniformly lethal disease, and there is an urgent need for potent, mechanism-based therapies to improve survival, especially in patients with metastatic, inoperable tumors. Hedgehog (Hh) pathway activation is seen in the majority of pancreatic cancer cell lines, and in vitro growth can be profoundly inhibited by the Hh small molecule antagonist cyclopamine. A comprehensive preclinical analysis of Hh inhibitors in pancreatic cancer is proposed, using in vivo models that recapitulate the complexities of human pancreatic cancer progression. Low-passage cell lines have been established from resected human pancreatic cancers, and will be used for generating orthotropic xenografts in pancreata of athymic mice. Either cyclopamine or an orally bioavailable synthetic Hh inhibitor (Genentech, Inc.) will be administered as monotherapy for 28 days. Treatment efficacy versus control mice will be assessed at necropsy by objective gross and histopathologic parameters, including development of intra-abdominal metastases, and by survival analysis. Synergism between the Hh antagonists and an anti-metabolite (gemcitabine) will be assessed in a subset of xenografted cancers. A transgenic mouse model of pancreatic intraepithelial neoplasia and invasive pancreatic cancer has been developed by misexpression of oncogenic KRAS in the pancreas. The role of Hh signaling, including effects of inhibiting pathway during the multistage progression to invasive cancer, will be studied in this model. As a prelude to clinical trials, biomarkers that predict responsiveness to Hh antagonists will be defined by correlating in vitro therapeutic response with the expression of Hh pathway genes and to global expression profiles determined using oligonucleotide microarrays, in a panel of 50 pancreatic cancer cell lines. Based on the efficacy of Hh inhibitors in the preclinical studies and the identification of predictive biomarkers for response, Phase II clinical trials will be initiated in patients with unresectable pancreatic cancers using the orally bioavailable synthetic Hh inhibitors.